2829 results about "Carbon coating" patented technology

The invention relates to a lithium ion secondary battery, a positive electrode active material, and a power device. The lithium ion secondary battery comprises a positive pole piece, wherein the positive pole piece comprises a positive pole film layer; the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a mixture of a granular first lithium-containing phosphate material and a rod-shaped second lithium-containing phosphate material, and the first lithium-containing phosphate material and the second lithium-containing phosphate material have a diffraction peak A between 29 degrees and 30 degrees and a diffraction peak B between 25 degrees and 26 degrees in an X-ray diffraction pattern; the intensity ratio of the diffraction peak A to the diffraction peak B is IA / IB; the second lithium-containing phosphate material satisfies: 1.1 > = IA / IB > = 0.95; the IA / IB of the second lithium-containing phosphate material is greater than the IA / IB of the first lithium-containing phosphate material; the first lithium-containing phosphate material and the second lithium-containing phosphate material each contain a carbon coating layer, and the carbon coating amount in the first lithium-containing phosphate material is smaller than the carbon coating amount in the second lithium-containing phosphate material.

The invention relates to the field of lithium battery negative electrode materials, and particularly discloses a silicon-carbon composite negative electrode material for a lithium ion battery and a preparation method of the silicon-carbon composite negative electrode material. The method comprises the following steps: preparing a porous carbon substrate, and depositing silicon nanoparticles in pores and on the surface of the porous carbon substrate by adopting a fluidized bed chemical vapor deposition process and taking silane as a silicon source to obtain a silicon-carbon core material; continuously carrying out carbon coating on the surface of the silicon-carbon core material in the fluidized bed by taking acetylene as a carbon source to form a carbon coating layer; and leading out the obtained material from the fluidized bed, taking acetylene as a carbon source, and carrying out carbon coating on the surface of the primary carbon coating layer again by adopting the rotary furnace to form a secondary carbon coating layer. According to the preparation method, a porous carbon matrix and double-layer functional carbon coating process is adopted, so that the volume expansion of silicon in the circulation process is remarkably inhibited, the interface side reaction is reduced, and the circulation stability of the material is effectively improved.

The invention discloses a silicon-carbon negative electrode material and a preparation method and application thereof.The silicon-carbon negative electrode material comprises a porous carbon substrate, a silicon element distributed in pore channels of the porous carbon substrate and carbon coating the outer surfaces of the porous carbon substrate and the silicon element, the porous carbon substrate is prepared after two times of activating treatment, and the silicon element is prepared after two times of activating treatment. The porous carbon has dendritic pore channels and meets at least one of the following conditions: a, the volume ratio of micropores is 10-30%; b, the volume ratio of mesopores is 60-90%; c, the volume ratio of macropores is 0-10%; d, the specific surface area is not less than 200m < 2 > / g; e, the pore volume is not less than 0.4 cm < 3 > / g; and f, the average particle size D50 is 1-20 [mu] m. By activating the porous carbon substrate, more buffer spaces can be provided for volume expansion of nano silicon particles from the angle of substrate preparation, and the cycling stability of the silicon-carbon negative electrode material is remarkably improved.

The invention discloses a composite positive electrode material and a preparation method thereof, a positive plate and a lithium ion battery. The composite positive electrode material comprises lithium iron phosphate and a carbon coating layer coating the surface of the lithium iron phosphate, wherein the integral intensity ratio ID / IG of a D peak to a G peak of the carbon coating layer in a Raman spectrum is 0.2-0.9, and the resistivity of the composite positive electrode material is 0.1-10 omega.cm. According to the preparation method, the graphitization degree of the carbon coating layer is controlled within a proper range (ID / IG is 0.2-0.9), so that good conductivity is ensured, and structural instability caused by excessive graphitization is avoided. The moderate graphitization degree is beneficial to formation of an ordered carbon layer structure, provides more electron transport channels and reduces the potential barrier of electron migration, so that the conductivity of the composite material is greatly improved, and the resistivity is reduced to an excellent level of 0.1-10 omega.cm.

A composite positive electrode material, a preparation method therefor and the use thereof. The composite positive electrode material comprises an inner core and a carbon coating layer covering at least part of the surface of the inner core and / or embedded in the inner core; the inner core comprises NaFePO4 and a compound represented by formula 1; Na4+xFe3-y(PO4)2+zP2O7 formula 1, where -0.15≤x≤0.8, 0≤y≤0.5, and -0.2≤z≤0.2; the particle size of NaFePO4≤100 nm. When being used for batteries, the composite positive electrode material can improve the capacities and rate capabilities of the batteries.

The invention discloses a preparation method of a high-compaction lithium manganese iron phosphate positive electrode material, which comprises the following steps: placing a manganese source, an iron source and a phosphorus source in deionized water, stirring, carrying out primary high-speed ball milling, carrying out constant-temperature water bath, adding an oxidizing agent, stirring and oxidizing, and drying the slurry to obtain manganese iron phosphate precursor powder; carrying out primary sintering on the ferromanganese phosphate precursor powder to obtain a ferromanganese phosphate primary sintering material; putting the ferromanganese phosphate primary sintering material into deionized water, adding a lithium source and a carbon source at the same time, and performing stirring, secondary high-speed ball milling and drying to obtain lithium ferromanganese phosphate precursor powder; and carrying out secondary sintering on the lithium manganese iron phosphate precursor powder to obtain the high-compaction lithium manganese iron phosphate positive electrode material. The void ratio is well reduced and good carbon coating is realized by means of secondary grinding and secondary sintering, and compared with the prior art, the method has the advantages that good capacity can be maintained, the powder compaction density of the material can be improved, the conductivity can be improved, and the specific surface area of the material can be effectively reduced.

The invention discloses a lithium iron phosphate positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium iron phosphate positive electrode materials. The lithium iron phosphate positive electrode material comprises a lithium iron phosphate matrix and a carbon coating layer coating the surface of the lithium iron phosphate matrix, the average standard deviation of the thickness of a carbon coating layer in the lithium iron phosphate positive electrode material is # imgabs0 #, and sigma (d) is more than or equal to 0.05 nm and less than or equal to 0.35 nm; the average standard deviation of the carbon content in the lithium iron phosphate positive electrode material is sigma (Cwt%), and sigma (Cwt%) is larger than or equal to 0.02 wt% and smaller than or equal to 0.35 wt%. The lithium iron phosphate positive electrode material has a uniform carbon coating layer, and the thickness of the carbon coating layer and the carbon content at each position are relatively consistent, so that the improvement of the carrier mobility of the lithium iron phosphate positive electrode material is facilitated, and the further improvement of the electrochemical performance of a battery prepared from the lithium iron phosphate positive electrode material is facilitated.

The invention provides a preparation method of a porous carbon-silicon composite negative electrode material of a lithium battery. The preparation method comprises the following steps: constructing a multi-stage template system; carrying out carbon precursor impregnation and gradient temperature carbonization on the multistage template system; removing the template to form a gradient porous carbon carrier; carrying out gradient temperature zone silane deposition; and plasma-assisted carbon coating and nitrogen doping are carried out. According to the method, a silicon dioxide sphere hard template is combined with cetyltrimethylammonium bromide and a block copolymer soft template to form a porous carbon carrier with a micropore-mesopore-macropore three-stage structure, and gradient distribution of silicon in porous carbon is realized by utilizing a three-temperature-zone fluidized bed reactor and a pulse type deposition technology, so that the silicon-based porous carbon composite material is obtained. The problem of volume expansion of the silicon material is effectively relieved and the material cycling stability is improved. The porous carbon-silicon composite negative electrode material prepared by the invention has high specific surface area, excellent ion transmission channel and good structural stability, and can be applied to a high-energy-density lithium ion battery.

The invention provides a silicon-carbon negative electrode material and a preparation method thereof. The preparation method comprises the following steps: a) mixing a phenol monomer, an aldehyde solution, ammonia water and water, dropwise adding a boric acid solution for reaction, and curing to obtain boron-containing phenolic resin; b) carbonizing the boron-containing phenolic resin obtained in the step a), mixing with alkali, and activating to obtain boron-doped porous carbon; and c) carrying out silicon deposition on the boron-doped porous carbon obtained in the step b) by adopting a gaseous silicon source, carrying out carbon coating by adopting a gaseous carbon source, and cooling to obtain the silicon-carbon negative electrode material. Compared with the prior art, the preparation method provided by the invention has the advantages that a conductive network can be formed by doping the boron element, the electron concentration can be improved, the electron transfer rate is favorably improved, the conductivity of the material is effectively enhanced, and the rate capability of the negative electrode material is effectively improved; meanwhile, the residual carbon rate in the porous carbon preparation process can be greatly increased, and the cost of the whole silicon-carbon negative electrode material is effectively reduced.

The invention discloses a carbon-coated lithium iron phosphate active material and a preparation method thereof, a positive pole piece and a lithium battery, and relates to the technical field of lithium batteries. According to the method, the structure of the carbon coating layer of the carbon-coated lithium iron phosphate active material is comprehensively evaluated through the carbon coating factor beta, # imgabs0 can evaluate the amount of graphitized carbon on the unit surface area of the carbon-coated lithium iron phosphate active material, and compared with amorphous carbon, the graphitized carbon has more excellent conductivity and can better improve the conductivity of a lithium iron phosphate matrix. By regulating and controlling a carbon coating layer structure of the carbon-coated lithium iron phosphate active material, a carbon coating factor beta meets a specific value range, so that the uniform conductivity of the carbon-coated lithium iron phosphate active material is improved; the lithium ion battery prepared from the lithium ion battery positive electrode material is small in internal resistance growth rate, charge transfer impedance Rct sample standard deviation and Warburg coefficient sample standard deviation, and the overall electrical performance of the lithium ion battery is improved.

The invention provides a lithium-rich lithium ferrite material and a preparation method and application thereof, the lithium-rich lithium ferrite material comprises a core layer and a carbon coating layer, the core layer is doped lithium-rich lithium ferrite, the chemical formula of the doped lithium-rich lithium ferrite is Li < 5 > Fe < 1-x > Al < x > O < 4 >, and x is 0.003-0.030. The lithium-rich lithium ferrite material is high in structural stability and excellent in conductivity; as a lithium supplement additive of a positive electrode active material, the composite material can improve electrochemical performance such as high-temperature storage performance and normal-temperature cycle performance of a lithium ion battery.

The invention relates to a silicon-carbon composite material and a preparation method and application thereof.The preparation method comprises the steps that a porous graphite raw material is subjected to acid pickling and smashing to obtain pretreated porous graphite, then the pretreated porous graphite is soaked in a carbon precursor solution in a vacuum mode, carbonization treatment is conducted after centrifugal separation, pores of the porous graphite are filled with carbides, physical activation is conducted, and the silicon-carbon composite material is obtained; the preparation method comprises the following steps: forming pores in a carbide to form a graded pore structure to obtain a porous graphite composite material, then carrying out silicon deposition in a fluidized bed to obtain a uniform nano silicon layer, and then carrying out carbon coating treatment to obtain a silicon-carbon composite material; the graphite with relatively low cost is adopted as a matrix, high capacity and long cycle performance of the graphite-based silicon-carbon negative electrode material are realized through hierarchical pore structure design, carbonization-activation synergistic pore forming and interface deposition process optimization, and the graphite-based silicon-carbon negative electrode material can be applied to the fields of power batteries and high-energy-density energy storage, especially the field of lithium ion batteries and has wide application prospects. The expansion rate of the battery can be reduced, and the specific capacity, cycling stability and safety of the lithium ion battery can be improved.

The invention discloses a lithium manganese iron phosphate composite material, a preparation method thereof and a lithium ion battery containing the lithium manganese iron phosphate composite material. The preparation method comprises the following steps: grinding, sintering and crushing a mixture of the lithium iron manganese phosphate, the lithium iron phosphate precursor and water to form the lithium iron manganese phosphate composite material, the sintering temperature is 650 DEG C to 750 DEG C; wherein the lithium manganese iron phosphate forms an inner core of the lithium manganese iron phosphate composite material, and the average particle size of the inner core is 600 nm to 1200 nm; the lithium iron phosphate precursor forms a lithium iron phosphate coating layer and a carbon coating layer of the lithium manganese iron phosphate composite material. The lithium manganese iron phosphate composite material provided by the invention can effectively improve the ginger-Taylor effect of the lithium manganese iron phosphate and improve the electrochemical cycle performance of the material at the same time.

The invention relates to the technical field of lithium ion battery silicon-carbon coating, in particular to a silicon-carbon composite material, a silicon-carbon negative electrode material, a preparation method of the silicon-carbon negative electrode material and a battery. The preparation method of the silicon-carbon composite material comprises the following steps: S1, mixing porous carbon and a gaseous organic silicon source for reaction under the conditions of 450-550 DEG C and 100-200 kPa; s2, under the condition of 500-800 DEG C, carrying out carbon coating on the product obtained in the step S1 by using a carbon source to obtain a silicon-carbon composite material; the flow velocity of the gaseous organic silicon source is 12-30L / min. The silicon-carbon composite material provided by the invention has good conductivity, and the subsequently prepared silicon-carbon negative electrode material and battery material have good electrochemical performance.

The present disclosure relates to the field of sodium-ion battery technology, and specifically, to a method for preparing carbon-coated sodium iron fluorophosphate from waste lithium iron phosphate and the application thereof. The method for preparing carbon-coated sodium iron fluorophosphate from waste lithium iron phosphate includes: mixing a waste lithium iron phosphate material with an alkaline solution for reaction, followed by solid-liquid separation, to obtain an aluminum-containing filtrate and a lithium iron phosphate filter residue; mixing the lithium iron phosphate filter residue, aluminum chloride and sodium chloride uniformly, followed by vacuum calcination, to obtain a calcination material; and mixing the calcination material with at least one of a sodium source, an iron source and a phosphorus source uniformly to obtain a mixture to which a fluorine source, a carbon source and a solvent are added for uniformly mixing, followed by drying and calcination sequentially to obtain the carbon-coated sodium iron fluorophosphate. The method has the advantages of low costs, a high added value, a short process, and a high recovery rate, and the carbon-coated sodium iron fluorophosphate obtained from the method has excellent electrochemical performance.

Provided are a lithium manganese iron phosphate material and a preparation method therefor, a positive electrode sheet, and a lithium ion battery. The lithium manganese iron phosphate material comprises a core and a coating layer that coats the surface of the core. The chemical formula of the material of the core is LiaMnbFecMdPO4, wherein M comprises at least one element among magnesium, calcium, strontium, cobalt, titanium, zirconium, molybdenum, vanadium, niobium, nickel, scandium, chromium, copper, zinc, beryllium, lanthanum and aluminum. The coating layer is formed by sintering a carbon source, and the carbon coating layer comprises graphitized carbon.

The invention belongs to the technical field of semiconductors, and particularly relates to a gradient transition composite tantalum carbide coating and a preparation method thereof.The gradient transition composite tantalum carbide coating is located on the surface of a graphite substrate material and sequentially comprises a pyrolytic carbon coating, a tantalum carbide-pyrolytic carbon composite coating and a tantalum carbide coating from inside to outside; wherein the thermal expansion coefficient of the pyrolytic carbon coating is 2.5-4.5 * 10 <-6 > / K, the thermal expansion coefficient of the composite coating is 4.5-6.0 * 10 <-6 > / K, and the thermal expansion coefficient of the tantalum carbide coating is 6.1-8.0 * 10 <-6 > / K. According to the gradient transition structure of the coating, the problem that thermal expansion coefficients between the coating and a base body are not matched is solved, the thermal shock resistance of the coating is effectively improved, meanwhile, the pinning effect can be achieved, the adhesive force between the coatings is enhanced, and the service life of a product is prolonged; compared with a single tantalum carbide coating, crack accumulation and through holes cannot be generated.

The invention relates to a preparation method and application of a composite porous carbon-based negative electrode material with soft carbon coated with hard carbon. The preparation method comprises the following steps: (S1) carbonizing and activating a soft carbon material precursor to obtain soft carbon core particles; (S2) carrying out graft modification on the oxidized soft carbon inner core particles through dopamine polyethylene glycol silane, and then carrying out in-situ copolymerization reaction on the modified soft carbon inner core particles and dopamine to obtain organic silicon-polydopamine coated soft carbon composite particles; (S3) carrying out in-situ polymerization of phenolic aldehyde on the surfaces of the composite particles to form phenolic aldehyde coated soft carbon composite particles; (S4) carbonizing and activating the phenolic aldehyde coated soft carbon composite particles to obtain hard carbon coated soft carbon composite porous carbon; and (S5) carrying out silicon deposition and carbon coating on the composite porous carbon to obtain the composite porous carbon-based negative electrode material with soft carbon coated with hard carbon. When the composite porous carbon-based negative electrode material with the soft carbon coated with the hard carbon prepared by the invention is applied to a negative electrode of a lithium battery, the composite porous carbon-based negative electrode material has good electrochemical performance, and particularly has excellent cycle performance and compression resistance.

The invention relates to the technical field of electrode materials, in particular to a silicon-carbon negative electrode material and a preparation method and application thereof. The silicon-carbon negative electrode material comprises a plurality of silicon-carbon composite particles, each silicon-carbon composite particle comprises porous carbon, nano silicon particles and phosphorus element which are attached in pores of the porous carbon, and coating carbon for coating the porous carbon, and n-type doping of the phosphorus element is formed at the joint of the nano silicon particles and the porous carbon. The preparation method comprises the following steps: (1) adsorbing phosphoric acid in porous carbon, and carrying out a heating reaction in a protective gas atmosphere to generate phosphorus-infiltrated porous carbon; (2) introducing a gaseous silicon source in a protective gas atmosphere, and carrying out silicon deposition on the phosphorus-infiltrated porous carbon by adopting a chemical vapor deposition method to obtain a phosphorus-doped silicon carbon material; and (3) carrying out carbon coating on the phosphorus-doped silicon carbon material to obtain the phosphorus-doped silicon carbon material. According to the method, the rate capability of the silicon-carbon negative electrode material can be remarkably improved while high first efficiency and high gram capacity are ensured.

The invention discloses a silicon carbon material, a preparation method thereof and a lithium ion battery. The preparation method of the silicon-carbon material comprises the following steps: S1, adding an alkaline reagent into a mixed solution containing a porous carbon-loaded silicon substrate, transition metal salt and a solvent, and drying to obtain a first precursor; s2, performing carbon deposition on the first precursor by adopting a chemical vapor deposition method, performing in-situ growth of a carbon nanotube, and then performing acid pickling and drying to obtain a second precursor; s3, performing silicon deposition on the second precursor by adopting a chemical vapor deposition method, and forming silicon nanoparticles and / or silicon nanowires in the carbon nanotubes in situ to obtain a third precursor; and S4, carrying out carbon coating on the third precursor to obtain the silicon carbon material. The silicon-carbon material is excellent in expansion inhibition performance and compressive strength and has excellent conductivity, and the lithium ion battery containing the silicon-carbon material can give consideration to excellent capacity performance, rate performance and cycle performance.

The invention provides a double-layer carbon-coated lithium iron phosphate composite material as well as a preparation method and application thereof. The double-layer carbon-coated lithium iron phosphate composite material comprises lithium iron phosphate and a carbon coating layer coating the surface of the lithium iron phosphate, the carbon coating layer comprises a first carbon coating layer and a second carbon coating layer, the ID / IG of the first carbon coating layer is smaller than that of the second carbon coating layer, the ID / IG of the second carbon coating layer is smaller than that of the first carbon coating layer, and the ID / IG of the second carbon coating layer is smaller than that of the second carbon coating layer. ID / IG refers to a peak intensity ratio of a D peak to a G peak in Raman spectra of the first carbon coating layer and the second carbon coating layer. According to the double-layer carbon coated lithium iron phosphate composite material provided by the invention, the conductivity of lithium iron phosphate and the wettability of an electrolyte are improved, and the rate capability and the low-temperature performance of a battery are improved.

The invention relates to a silicon-carbon composite material capable of improving the cycling stability of a battery, a preparation method of the silicon-carbon composite material, a negative pole piece and a lithium ion battery. The carbon-silicon composite particle comprises a silicon-carbon inner core and a carbon coating layer, nano-silicon is attached in holes and / or on the surface of a porous carbon matrix to form the silicon-carbon inner core, and the carbon coating layer is coated on at least part of the surface of the inner core; the porous carbon matrix and the carbon coating layer are both doped with halogen. According to the silicon-carbon composite material, the electron conductivity of the silicon-carbon composite material is improved by doping the halogen in the porous carbon matrix inside the silicon-carbon composite material and the carbon coating layer outside the silicon-carbon composite material; and meanwhile, the porous carbon matrix, the inner core composed of the nano silicon and the carbon coating layer are mutually matched and have synergistic interaction, so that the volume expansibility and defects of the silicon-carbon composite material are reduced, and the cycle stability is improved.

The invention provides an in-situ modified lithium-rich manganese-based precursor and a preparation method and application thereof.The preparation method comprises the following steps that a nickel-cobalt-manganese mixed metal salt solution, a precipitator solution and a complexing agent solution are introduced into a base solution for a first coprecipitation reaction, and after the first coprecipitation reaction is finished, feeding is stopped; and introducing a doped nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, a complexing agent solution and a carbon source solution into a system after the first coprecipitation reaction is finished, and carrying out a second coprecipitation reaction to obtain the in-situ modified lithium-rich manganese-based precursor. According to the preparation method, doping elements and a carbon source are introduced when the lithium-rich manganese-based precursor is prepared through the coprecipitation reaction, in-situ uniform construction of oxygen vacancies and a carbon coating layer on the surface of the material is synchronously achieved, the in-situ modified lithium-rich manganese-based precursor is obtained, the treatment step of subsequent secondary coating can be reduced, the production cost can be reduced, and the method is suitable for industrial production. The technological process is shortened.

The invention provides a silicon-carbon composite material as well as a preparation method and application thereof. The silicon-carbon composite material comprises a porous carbon material; the silicon particles are distributed on the surface layer of the porous carbon material and in pore channels in the porous carbon material, the distribution concentration of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material, and the particle size of the silicon particles in the surface layer of the porous carbon material is smaller than that of the silicon particles in the porous carbon material; the silicon dioxide layer is formed on the surface of the silicon particles; and the carbon coating layer is formed on the surface of the silicon dioxide layer. The lithium ion battery prepared by taking the silicon-carbon composite material as a positive electrode active material shows good electrochemical performance, and has relatively high specific capacity, good cycling stability and rate capability.

The invention discloses a silicon-carbon material, a preparation method and application thereof and a lithium ion battery. The preparation method of the silicon carbon material comprises the following steps: S1, performing carbonization treatment and activation treatment on a mixture of a carbon source and transition metal salt to obtain porous carbon; s2, performing carbon deposition on the porous carbon by adopting a chemical vapor deposition method, and growing a carbon nanotube in situ to obtain a first precursor; s3, performing silicon deposition on the first precursor by adopting a chemical vapor deposition method to obtain a second precursor; s4, carrying out carbon coating on the second precursor; and carrying out acid pickling and drying to obtain the silicon-carbon material. The silicon-carbon material is relatively good in conductivity and pressure resistance and excellent in expansion inhibition performance, and the prepared lithium ion battery can give consideration to excellent first effect, gram volume, rate capability and cycle performance.

The invention discloses a graphite-doped negative electrode material as well as a preparation method and application thereof, and belongs to the technical field of rechargeable secondary battery negative electrode materials. The doped graphite negative electrode material comprises an inner core and a shell on the outer layer of the inner core, the inner core is an element-doped graphite-doped secondary particle; the doping mode of the doped graphite secondary particles is solid phase doping or liquid phase doping; the shell comprises an element-doped carbon coating layer formed by vapor deposition; and the total mass of the doped elements accounts for 0.5-10% of the mass of the doped graphite negative electrode material. According to the doped graphite negative electrode material provided by the invention, the graphite secondary particle core and the carbon coating layer are subjected to element doping treatment, the microstructure of graphite is improved by element doping, and active site defects are formed, so that the diffusion of a charge carrier is facilitated, and the dynamic performance of the material is improved; meanwhile, the graphite layer spacing is enlarged; the carbon coating layer isolates the graphite secondary particle inner core from being in direct contact with the electrolyte, so that the fast charging performance of the doped graphite negative electrode is comprehensively improved in an omnibearing and multi-angle manner.

The invention discloses a preparation method of a hard-soft carbon coated silicon-carbon negative electrode material, which comprises the following steps: S1, mixing nano silicon and graphite to obtain silicon-carbon mixed powder; s2, dissolving asphalt in absolute ethyl alcohol, then mixing with the silicon-carbon mixed powder, and carrying out carbonization treatment; s3, dissolving sucrose in water, then mixing with the composite material obtained in S2, and performing carbonization treatment to obtain a hard-soft carbon coated silicon carbon negative electrode material; wherein the carbonization temperature in the step 2 and the carbonization temperature in the step 3 are both 1200-1300 DEG C. According to the hard-soft carbon coated silicon-carbon negative electrode material and the preparation method thereof, the mixture of silicon and graphite is subjected to soft carbon coating and hard carbon coating through asphalt and cane sugar in sequence, so that the obtained hard-soft carbon coated silicon-carbon negative electrode material not only can inhibit volume expansion of silicon, but also shows excellent rate capability and cycle performance.

The invention belongs to the technical field of lithium batteries, and discloses a fluorine-doped lithium iron manganese phosphate positive electrode material and a preparation method thereof.The preparation method comprises the steps that hydrofluoric acid, manganese sulfate monohydrate, ferrous sulfate heptahydrate, lithium hydroxide monohydrate and phosphoric acid serve as raw materials, and a fluorine-doped lithium iron manganese phosphate precursor is prepared through a microwave-hydrothermal synthesis method; and forming a coating layer on the surface of the precursor by using SnO2-doped chitosan gel, and calcining to obtain the fluorine-doped lithium iron manganese phosphate positive electrode material. The positive electrode material comprises fluorine-doped lithium manganese iron phosphate particles and a SnO2 / C coating layer, doping of fluorine promotes diffusion of lithium ions of the positive electrode material, the structure of the material is more stable, SnO2 is doped in chitosan serving as a carbon source, the conductivity of the positive electrode material is improved, and on the basis of the synergistic effect of the fluorine element and metal ions of the coating layer, the conductivity of the positive electrode material is improved. A uniform and tightly combined carbon coating layer is formed on the surface of the material. The fluorine-doped lithium iron manganese phosphate positive electrode material prepared by the preparation method has excellent cycle performance and rate capability.

The invention provides a modified lithium iron manganese phosphate positive electrode material and a preparation method thereof, a positive plate and a lithium ion battery. The modified lithium manganese iron phosphate positive electrode material comprises transition metal element-doped lithium manganese iron phosphate and a silicon hydroxyl-containing carbon coating layer, wherein the surface of the transition metal element-doped lithium manganese iron phosphate is coated with the silicon hydroxyl-containing carbon coating layer. And the transition metal element replaces the position of an iron element in the lithium manganese iron phosphate, so that the ion diffusion coefficient of the lithium manganese iron phosphate and the compaction density of the modified lithium manganese iron phosphate positive electrode material can be improved. The existence of the silicon hydroxyl-containing carbon coating layer is beneficial for improving the electronic conductivity and the structural stability of the lithium manganese iron phosphate positive electrode material, so that the manganese dissolution rate of the lithium manganese iron phosphate positive electrode material in the high-temperature cycle process of the battery is reduced. Therefore, the modified lithium manganese iron phosphate positive electrode material disclosed by the invention has relatively high ion diffusion coefficient, electronic conductivity, compaction density, rate capability, energy density and cycling stability.

The invention belongs to the technical field of sodium ion batteries, and mainly relates to a multi-metal element in-situ doped sodium ferric sulfate positive electrode material prepared from byproduct sulfate, a method thereof and a sodium ion battery. The method comprises the following steps: adding solid waste sodium sulfate, anhydrous sodium sulfate, by-product ferrous sulfate and ferrous sulfate heptahydrate into deionized water, stirring until the mixture is fully dissolved, and filtering and separating insoluble substances to obtain a sodium ferric sulfate precursor solution; adding an organic carbon source and an inorganic carbon source into the precursor solution, fully stirring and mixing, and performing spray drying to obtain a precursor; and sintering the precursor in an inert atmosphere to obtain the multi-metal element in-situ doped sodium ferric sulfate positive electrode material. According to the method, two byproducts sodium sulfate and ferrous sulfate are utilized, and an organic carbon source and an inorganic carbon source are matched for use to obtain a carbon-coated material, so that the cost of a sodium ferric sulfate raw material of a sodium-ion battery is reduced to the greatest extent, and the sodium ferric sulfate positive electrode material with ultralow cost and good electrochemical performance is prepared.